Cadmium sulfide is a known semi-conductor material available conventionally in crystalline form. Cadmium sulfide crystals can be used for various semi-conductor applications and are normally grown by crystalline growth by withdrawing a seed crystal from a molten pool of elemental cadmium sulfide heated to liquid form. Cadmium sulfide can be fabricated into wafers or other materials having various uses in semi-conductor and integrated circuit technologies.
Cadmium sulfide crystals have also been investigated for various practical applications. Various investigators have created the possible use of polished cadmium sulfide single crystals for applications in laser development. Aasov investigated pulsed two-photon optical pumping in polished cadmium sulfide crystals forming a Fabry-Perot cavity which was investigated for its laser activity. Fuchs et al. developed an argon pumped CW-CdS platelet ring laser with the hope of combining the advantages of an increased spectral range over dye lasers and with the possibility of intra-cavity tuning elements which were not yet available in semi-conductor diode lasers at the time. Other investigators reported that Xenon flash-induced lasing could be created in cooled cadmium sulfide single crystal and electron beam pumped uncooled multi-element cadmium sulfide lasers were reported. Unfortunately, the low lasing efficiency and optical damage place the cadmium sulfide material in a category far from commercial application and comparatively unattractive in comparison to other lasing materials.
It has been previously demonstrated that dilute colloidal suspensions of extremely small cadmium sulfide particles have been created which exhibit unique and interesting size quantization effects. See Henglein "Mechanism of Reactions on Colloidal Microelectrodes and Size Quantitation Effects," Topics in Current Chemistry, Vol. 143, pp. 115-116, 129-132, 165-180 (1988). These particles are referred to as "Q" particles. These size-quantization effects become noticeable when the particle size is comparable or smaller than the diameter of the exciton in a semi-conductor macrocrystal. Dilute colloidal suspensions of Q-CdS particles can be shown to have unique quantum mechanical behavior deriving from the extremely small particle size which can be observed by their ultraviolet and visible and luminescence spectra which can be observed in aqueous suspension.